Motor having suction ring

ABSTRACT

A suction ring is fixed to a motor base and is provided with an outer circumferential section having a first outer diameter that is smaller than an inner diameter of a wall section of the motor base. A plurality of protruded sections each have a second outer diameter larger than the inner diameter of the wall section of the motor base and protrudes outward in a radial direction from the outer circumferential section of the suction ring. The plurality of protruded sections of the suction ring are press fitted into a wall section of the motor base and secures the suction ring to the motor base. One surface of the suction ring coincides with a bottom surface of the ring magnet covering a whole range of a projected area of the ring magnet that is projected onto the surface of the suction ring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending application Ser. No.11/425,195 filed on Jun. 20, 2006 (allowed), and for which priority isclaimed under 35 U.S.C. § 120; and this application claims priority ofApplication No. 2005-191317 filed in Japan on Jun. 30, 2005 under 35U.S.C. § 119; the entire contents of all are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a motor having a suction ring,particularly, relates to a motor having a suction ring suitable fordriving a hard disc drive and a laser beam printer.

2. Description of the Related Art

A motor for driving a hard disc drive (hereinafter referred to as HDD)according to the prior art is shown in FIG. 5.

FIG. 5 is a cross sectional view of a motor according to the prior art,and FIG. 6 is a plan view of a suction ring to be used in the motorshown in FIG. 5.

In FIG. 5, a motor 150 is driven by three-phase current and mounted withat least one hard disc (HD) 101 thereon.

Further, the motor 150 is essentially composed of a stator S1 and arotor R1.

The stator S1 is further composed of a core 106, a coil 107, a counterplate 109, a sleeve 110 and a motor base 105. The motor base 105 isformed by a process of pressing an aluminum plate or an aluminumdie-casting process.

The sleeve 110 is in a cylindrical shape and fixed on a circumferentialwall surface of a hole formed vertically in the center of the motor base105 by a binding agent or a press fitting process.

Further, an inner circumferential section of the sleeve 110 is made froma sintered metal material or a plated copper alloy material.

Furthermore, one end portion of the sleeve 110 is formed with a steppedsection for containing a thrust ring 112 to be detailed and the endportion is sealed by the counter plate 109.

As mentioned above, the motor 150 is driven by the three-phase current,so that the core 106 is provided with nine protrusions equivalent tomagnetic poles and formed in approximately an annular shape.

More specifically, the core 106 is formed by laminating a plurality ofsilicon steel plates and a surface of the core 106 is treated byinsulation coating through a process such as electropainting and powdercoating.

Further, each protrusion of the core 106 is wound up by the coil 107.

Furthermore, a terminal 107 a of a winding wire of the coil 107 issoldered on a flexible printed circuit board (hereinafter referred to asFPC) 114 mounted on a bottom of the motor base 105 by way of a throughhole 121.

On the other hand, the rotor R1 is further composed of a hub 102, ashaft 113 and a magnet 108.

The hub 102 and the shaft 113 are made from a stainless steel materialthrough a cutting process.

The magnet 108 is formed in a ring shape (hereinafter referred to asring magnet 108) and made from an Nd—Fe—B system material. A surface ofthe ring magnet 108 is treated by an electropainting process.

Further, the shaft 113 is fixed to the hub 102 through a process ofpress fitting and then adhered.

Furthermore, the ring magnet 108 is fixed on an inner surface of anouter circumferential section of the hub 102 by a binding agent.

In addition thereto, the motor 150 is provided with a thrust dynamicpressure fluid bearing SB1 and radial dynamic pressure fluid bearingsRB11 and RB12.

The thrust dynamic pressure fluid bearing SB1 is constituted by thethrust ring 112 in an annular shape that is fixed on a lower end portionof the shaft 113, the sleeve 110, the counter plate 109 and lubricatingfluid (hereinafter referred to as lubricant) that is filled among eachmember.

The thrust ring 112 is made from a stainless steel material or a copperalloy. In case the thrust ring 112 is made from a copper alloy, surfacesof the thrust ring 112 are nickel-plated.

Under the above-mentioned configuration, the thrust dynamic pressurefluid bearing SB1 sustains the rotor R1 in the thrust direction bygenerating dynamic pressure in the thrust direction by means of dynamicpressure grooves formed on both the top and bottom surfaces of thethrust ring 112 while the rotor R1 is rotating.

On the other hand, the radial dynamic pressure fluid bearings RB11 andRB12 are constituted by an outer circumferential surface of the shaft113, an inner circumferential surface of a through hole of the sleeve110 into which the shaft 113 is inserted, and lubricant filled in a gapbetween them.

At least either one of the outer circumferential surface of the shaft113 and the inner circumferential surface of the sleeve 110 is formedwith radial dynamic pressure grooves such as herringbone for generatingdynamic pressure. The dynamic pressure grooves generate dynamic pressurein the radial direction while the rotor R1 is rotating, and result insustaining the rotor R1 in the radial direction. Two groups of radialdynamic pressure grooves are provided at two individual positions beingapart from each other along the axis of rotation.

Further, the inner circumferential section of the sleeve 110 is madefrom a sintered material or a plated copper alloy material, as mentionedabove, and provided with a recessed portion that is disposed between thetwo individual positions being formed with radial dynamic pressuregrooves. In some cases, the sleeve 110 is divided into two components.

As mentioned above, the gap between the shaft 113 and the sleeve 110 andeach gap among the thrust ring 112, the sleeve 110 and the counter plate109 are filled with lubricant such as lubrication oil. The lubricant iscirculated by the revolution of the rotor R1, and resulting ingenerating dynamic pressure. By the dynamic pressure, each dynamicpressure fluid bearing sustains the rotor R1 to be rotatable freely.

In the meantime, the motor 150 is installed with a suction ring 111 thatis formed in a flat annular shape and disposed on the top surface of themotor base 105. A plan view of the suction ring 111 is shown in FIG. 6.Such a motor installed with a suction ring is disclosed in the Japanesepublication of unexamined patent applications No. 2003-61305.

The suction ring 111 is made from iron that is a magnetic material anddisposed under the ring magnet 108 so as to confront at least a part ofthe suction ring 111 with the bottom surface of the ring magnet 108.

Accordingly, the rotor R1 is magnetically absorbed toward the stator S1side and restricted its movable distance in the axial direction.

Installing such a suction ring enables to ensure higher anti-vibrationability and higher impact resistant, which are particularly required fora motor to be installed in an HDD.

In case such a suction ring is adhered on a motor base by using abinding agent, the suction ring may rise or slant with respect to themotor base due to shrinkage of the binding agent when hardening.

If such rising of the suction ring occurs, uniform suction force is notensured, and resulting in generating a problem of deteriorating noiselevel and vibration level of the motor.

Further, if the rising of the suction ring is excessively increased, thesuction ring possibly contacts with a ring magnet and adds rotationalload to the rotor, and resulting in generating another problem ofincreasing power consumption of the motor.

In this connection, it is commonly adopted as a method for installing asuction ring not to rise that an outer circumferential section of thesuction ring is press fitted to an inner surface of a circular wallsection provided for the motor base.

However, such a press fitting method creates further problems to bementioned next, so that the method has been desired to be improved.

Generally, a binding agent is used for fixing several componentstogether when assembling a motor. In order to harden the binding agentcompletely and to prevent so-called “out-gas” phenomenon that is aphenomenon of generating gas from the hardened binding agent with time,a treatment of so-called burning is applied to a motor, wherein thetreatment of burning is such as leaving a motor after assembled in ahigh temperature ambience of 130° C.

As mentioned above, the motor base is made from aluminum. A coefficientof linear expansion of the aluminum is 23.5×10⁻⁶/° C. On the contrary,the suction ring is made from iron, and a coefficient of linearexpansion of the iron is 12.1×10⁻⁶/° C. As a matter of fact, eachcoefficient of linear expansion extremely differs from each other.

Accordingly, dimensional change in the radial direction caused bythermal expansion extremely reduces an overlap width for press fittingbetween the motor base and the suction ring, and resulting in generatinga furthermore problem of rising the suction ring unless each overlapwidth of the suction ring and the motor base is designated to be morethan a prescribed value.

As a specific example, with respect to a suction ring having a thicknessof 0.4 mm, in case a diameter of an outer circumferential section of thesuction ring to be press fitted into a motor base is designated to be 20mm, an overlap width for press fitting disappears during the treatmentof burning, and resulting in raising the suction ring unless the suctionring is press fitted into the motor base with being previously providedwith an overlap width of 25 μm or more in diameter at the normaltemperature (20° C.).

However, in order to actually press fit the above-mentioned memberswhile maintaining the overlap width of 25 μm or more in diameter forpress fitting, it is necessary for press fitting pressure to be morethan 86 N. Enabling such a press fitting process of more than 86 Nrequires a relatively large-scale facility. In some cases, the motorbase is deformed by such a high press fitting pressure, and resulting indeteriorating noise level and vibration level of a motor to beassembled.

Further, in case the suction ring is press fitted by such a high pressfitting pressure, the suction ring disables to be accurately disposed ina prescribed position, and resulting in making a distance between thering magnet and the suction ring uneven. Under such a circumstance, amovable distance in the axial direction of the rotor fluctuates, andresulting in generating a more problem of deteriorating noise level andvibration level of the motor.

In case the press fitting pressure is 20 N or less, the press fittingprocess enables to be performed by a regular facility.

In addition thereto, the pressure of 20 N or less is preferable becausedeformation of members other than the press fitted section never occursor deformation is extremely slight if occurred.

SUMMARY OF THE INVENTION

Accordingly, in consideration of the above-mentioned problems of theprior arts, an object of the present invention is to provide a motorhaving a suction ring, which is less in noise and vibration andexcellent in rotational characteristics although the suction ring, whichconfronts with a ring magnet and absorbs a rotor, is press fitted into amotor base.

In order to achieve the above object, the present invention provides,according to an aspect thereof, a motor comprising: a rotor having a huband a ring magnet being fixed to the hub; and a stator having a motorbase and a suction ring in an annular shape made from a magneticmaterial being fixed to the motor base, wherein the rotor is sustainedrotatable freely with respect to the stator through a bearing composedof a sleeve and a shaft being inserted into the sleeve; wherein thesuction ring is provided with a plurality of protruded sections thatprotrude in a radial direction on an outer circumferential section or aninner circumferential section of the suction ring; wherein the protrudedsections of the suction ring are press fitted into a wall section thatis provided on the motor base and resulting in fixing the suction ringto the motor base; and further wherein one surface of the suction ringis disposed so as to coincide with a bottom surface of the ring magnetwith covering a whole range of a projected area of the ring magnet thatis projected on the surface of the suction ring.

According to another aspect of the present invention, there provided amotor comprising: a rotor having a hub and a ring magnet being fixed tothe hub; and a stator having a motor base and a suction ring in anannular shape made from a magnetic material being fixed to the motorbase, wherein the rotor is sustained rotatable freely with respect tothe stator through a bearing composed of a sleeve and a shaft beinginserted into the sleeve; wherein the motor base is provided with aplurality of protruded sections that is formed on a surface of the motorbase in a radial direction with rising toward the hub side; wherein anouter circumferential section or an inner circumferential section of thesuction ring is press fitted into the plurality of protruded sections ofthe motor base and resulting in fixing the suction ring to the motorbase; and further wherein one surface of the suction ring is disposed soas to coincide with a bottom surface of the ring magnet with covering awhole range of a projected area of the ring magnet that is projected onthe surface of the suction ring.

Other object and further features of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view of a motor having a suction ring commonto first and second embodiments according to the present invention.

FIG. 2 is a plan view of a suction ring according to a first embodimentof the present invention.

FIG. 3 is a graph showing characteristics of motors according to thefirst embodiment of the present invention and a comparative exampleaccording to the prior art.

FIG. 4 is a plan view of a suction ring and a motor base related to thesuction ring according to a second embodiment of the present invention.

FIG. 5 is a cross sectional view of a motor according to the prior art.

FIG. 6 is a plan view of a suction ring used in the motor shown in FIG.5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

In reference to FIGS. 1-3, a motor having a suction ring according to afirst embodiment of the present invention is detailed next.

FIG. 1 is a cross sectional view of a motor having a suction ring commonto first and second embodiments according to the present invention,wherein reference sings in parenthesis are exclusively for a secondembodiment.

FIG. 2 is a plan view of a suction ring according to a first embodimentof the present invention.

FIG. 3 is a graph showing characteristics of motors according to thefirst embodiment of the present invention and a comparative exampleaccording to the prior art.

A motor having a suction ring according to the first embodiment of thepresent invention is a three-phase motor for driving a hard discinstalled in a hard disc drive (hereinafter referred to as HDD). Themotor is disposed in clean ambience of an HDD and rotates at least onehard disc mounted on a hub at a rotational speed of 5400 rpm.

In FIG. 1, a motor having a suction ring (hereinafter genericallyreferred to as motor) 50 is essentially composed of a stator S and arotor R. Descriptions are given to configurations of the stator S andthe rotor R first.

The stator S is further composed of a motor base 5, a sleeve 10 that isfixed to the motor base 5, a core 6 and a coil 7 that is wound aroundthe core 6.

The motor base 5 is formed through a cutting process of aluminumdie-casting. A center hole 5 b having a wall section 5 a that risesupright with surrounding the center hole 5 b is provided at the centerof the motor base 5.

The sleeve 10 is formed in a cylindrical shape having a through hole 10a and fixed to the center hole 5 b of the motor base 5 by adhering orpress fitting.

Further, the sleeve 10 is made form a copper based sintered alloymaterial or a stainless steel material.

Furthermore, one end portion of the through hole 10 a of the sleeve 10is provided with a stepped section 10 b having a plurality of steps forcontaining a thrust ring to be detailed.

The core 6 is formed in approximately an annular shape by laminating aplurality of thin plates made from a magnetic material such as siliconsteel plate.

Further, a surface of the core 6 is treated by insulation coatingthrough a process such as electropainting and powder coating.

As mentioned above, the motor 50 is driven by three-phase current, sothat the core 6 is provided with nine protruded magnetic poles. Eachprotruded magnetic pole is wound up by the coil 7 corresponding to eachphase.

Further, a terminal 7 a of a winding wire of the coil 7 is soldered on aflexible printed circuit board (hereinafter referred to as FPC) 14mounted on a bottom surface 5 d of the motor base 5 by way of a throughhole 5 c.

Furthermore, the FPC 14 is provided with a soldering section not shownfor soldering the terminal 7 a of the coil 7 thereon and a land sectionnot shown for electrically connecting the coil 7 to a driving circuitprovided in an HDD side. A wiring pattern electrically connects betweenthe soldering section and the land section.

On a top surface of the motor base 5, there is provided with a suctionring 11, which is made from iron, that is, a magnetic material andformed in an annular shape. The suction ring 11 is provided with aplurality of protruded sections in an outer circumferential section.Each protruded section is fixed to the motor base 5 by press fittingeach protruded section into a wall section 5 e that is provided on themotor base 5 in a circular wall shape. Further configurations of thesuction ring 11 will be detailed later on.

On the other hand, the rotor R is composed of a shaft 13, a hub 2 thatis formed in approximately a cup shape and a ring magnet 8 that isformed in an annular shape, wherein both of the shaft 13 and the ringmagnet 8 are fixed to the hub 2.

The shaft 13 is made from a stainless steel material.

The hub 2 is provided with an outer circumferential wall section 2 a, aflange 2 b, which protrudes outward from the outer circumferential wallsection 2 a and is loaded with a hard disc 1, and a through hole 2 c,wherein the hub 2 is made from a stainless steel material through acutting process.

The ring magnet 8 is made from an Nd—Fe—B system material and itssurface is nickel plated.

Further, an inner circumferential section of the ring magnet 8 ismagnetized in 12 magnetic poles.

One end portion of the shaft 13 is fixed to the through hole 2 c of thehub 2 by means of a process of press fitting or welding.

In addition, the ring magnet 8 is fixed on an inner circumferentialsurface of the outer circumferential wall section 2 a of the hub 2.

As mentioned above, since the hub 2 is made from a stainless steelmaterial, that is, a magnetic material, the hub 2, the core 6 and thering magnet 8 result in constituting a magnetic circuit.

Further, the shaft 13 fixed to the rotor R is inserted into the throughhole 10 a of the sleeve 10 fixed to the stator S.

In this connection, the rotor R is sustained rotatable freely withrespect to the stator S through a bearing when electric current from adriving circuit installed in an HDD side is supplied to each phase ofthe coil 7.

Succeedingly, the bearing is detailed.

The motor 50 is provided with radial dynamic pressure fluid bearings RB1and RB2 and a thrust dynamic pressure fluid bearing SB.

The radial dynamic pressure fluid bearings RB1 and RB2 are constitutedby an outer circumferential surface 13 a of the shaft 13, an innercircumferential surface 10 a 1 of the through hole 10 a of the sleeve 10and lubricating fluid (hereinafter referred to as lubricant) 20 that isfilled in a gap between the outer circumferential surface 13 a of theshaft 13 and the inner circumferential surface 10 a 1 of the throughhole 10 a.

At least either one of the outer circumferential surface 13 a and theinner circumferential surface 10 a 1 is formed with two groups of radialdynamic pressure grooves 16, which are allocated at individual positionsin the axial direction. The radial dynamic pressure grooves 16 are sucha groove as herringbone.

A taper section 23 is provided on a top end portion toward the hub 2side of the through hole 10 a of the sleeve 10, wherein a diameter ofthe taper section 23 increases in accordance with approaching a top endsurface of the sleeve 10.

Further, a gap 22 is provided between the top end surface of the sleeve10 and a bottom surface 2 d of the hub 2.

An amount of the lubricant 20 to be filled is controlled such that afluid level of the lubricant 20 positions in a middle of the tapersection 23. Consequently, the taper section 23 is provided with afunction of preventing the lubricant 20 from leaking out as a role of aso-called taper seal section.

Furthermore, providing the gap 22 between the sleeve 10 and the hub 2prevents the lubricant 20 from leaking out or scattering moreeffectively.

By the radial dynamic pressure fluid bearings RB1 and RB2, the rotor Ris sustained in the radial direction with respect to the stator Sthrough dynamic pressure that is generated by the radial dynamicpressure grooves 16 in accordance with revolution of the rotor R.

On the other hand, the thrust dynamic pressure fluid bearing SB isconstituted by a thrust ring 12 that is fixed to a bottom end portion ofthe shaft 13 and contained in the stepped section 10 b of the sleeve 10,a counter plate 9 that is fixed to the stepped section 10 b of thesleeve 10 and seals a bottom end section of the through hole 10 a, andthe lubricant 20 that is filled in gaps among each member.

At least either one of a top surface of the thrust ring 12 and a bottomend surface of the sleeve 10, which confronts with the top surface ofthe thrust ring 12, and at least either one of a bottom surface of thethrust ring 12 and a top surface of the counter plate 9, which confrontswith the bottom surface of the thrust ring 12, are formed with thrustdynamic pressure grooves not shown such as herringbone.

By the thrust dynamic pressure fluid bearing SB, the rotor R issustained in the thrust direction with respect to the stator S throughdynamic pressure that is generated by the thrust dynamic pressuregrooves in accordance with revolution of the rotor R.

With referring to FIG. 2, an actual configuration of the suction ring 11and a method of installing the suction ring 11 to the motor base 5 aredepicted next.

A shape and disposition of the suction ring 11 is decided such that apart of a top surface of the suction ring 11 confronts closely with abottom surface 8 a of the ring magnet 8 when the rotor R is mounted onthe stator S. By this configuration, the rotor R is magneticallyabsorbed toward the stator S side.

In the first embodiment of the present invention, as shown in FIG. 2,the suction ring 11 is provided with six protruded sections 11 a, whichprotrude outward in the radial direction in an outer circumferentialsection of the suction ring 11, at an equiangular interval.

More specifically, the suction ring 11 is a thin plate in an annularshape made from iron, wherein a thickness of the suction ring 11 is 0.4mm, an outer diameter φ₁ is 20 mm and an inner diameter φ₂ is 16 mm.

Further, an outer diameter φ₃ of each protruded section 11 a is 21 mmand a tip width “d” in a circumferential direction of a tip portion ofthe protruded section 11 a is 1.5 mm.

Furthermore, both ends of the tip portion of the protruded section 11 aare gradually connected to an outer circumferential surface of thesuction ring 11 itself by means of a curved section 11 a 1.

The suction ring 11 is fixed to the motor base 5 by press fitting thesesix protruded sections Hal into an inner circumferential surface of thewall section 5 e of the motor base 5.

In the case of the suction ring 11 according to the first embodiment ofthe present invention, an overlap width for press fitting is designatedto be 25 μm in diameter.

In this connection, it never occurs to the suction ring 11 that anoverlap width disappears due to thermal expansion in the radialdirection of the suction ring 11 and the motor base 5 and resulting inraising the suction ring 11.

As mentioned above, the suction ring 11 is provided with six protrudedsections 11 a and the tip width “d” of each protruded section 11 a isdesignated to be 1.5 mm.

Further, a ratio of a length L1 in a circumferential direction of theprotruded sections 11 a to be press fitted, that is, a total length ofthe tip width “d” to a total circumferential length L of the suctionring 11 is minimized.

Accordingly, the suction ring 11 and the motor base 5 other than asection to be press fitted enable to be released from deformation.

More specifically, in the first embodiment of the present invention, thetotal circumferential length L of the suction ring 11 is “φ₃×π=21mm×π≈66.0 mm” and the length L1 of the tip width “d” of the protrudedsections 11 a is “1.5 mm×6=9 mm”, so that the ratio of L1 to L is“9/66.0=13.6(%)”. Consequently, press fitting pressure of the suctionring 11 according to the first embodiment becomes 11.7 N, which isapproximately 13.6% of 86 N that is the press fitting pressure basedupon the prier art, wherein a suction ring according to the prior art isprovided with no protruded sections and press fitted to a motor base. Asa result, deformation of the suction ring 11 or the motor base 5 doesnot become a problem.

A plurality of suction rings having an individual outer diameter isproduced, and a relationship between an overlap width for press fittingand press fitting pressure is measured with respect to each suctionring. A result of measurement is shown in FIG. 3. In FIG. 3, acomparative example denotes a conventional motor according to the priorart, wherein the suction ring according to the prior art is providedwith no protruded sections, and whole range of the outer circumferenceof the suction ring is press fitted into the motor base totally.

In FIG. 3, as mentioned above, the suction ring 11 according to thefirst embodiment of the present invention exhibits 11.7 N of pressfitting pressure at 25 μm of the overlap width for press fitting.

Further, an overlap width for press fitting, which ensures preferablepress fitting pressure of 20 N or less, is 40 μm or less.

Accordingly, the above-mentioned rising of the suction ring caused bythermal expansion never occurs. A range of overlap width, which does notdeform a motor base other than a section to be press fitted, isdesirable to be 25 to 40 μm.

In this connection, an upper limit of the overlap width is determined bythe ratio of the length L1 of the protruded sections 11 a in thecircumferential direction to the total circumferential length L of thesuction ring 11, that is, the ratio of L1 to L. Consequently, it isenough for determining an upper limit of an overlap width that anoverlap width, which ensures press fitting pressure of 20 N or less, isdesignated to be an upper limit in accordance with the ratio of L1 to L.

As shown in FIG. 2, the suction ring 11 has a width “w”, wherein“w=(φ₁−φ₂)/2”. The width “w” is wider than a width “wt” of a projectedarea T of the ring magnet 8, wherein the projected area T is a range ofthe ring magnet 8 that is projected on the surface of the suction ring11. The suction ring 11 is formed in an annular shape so as to contain awhole range of the projected area T of the ring motor 8 on the surfaceof the suction ring 11 and mounted on the motor base 5. Consequently, nomatter how the rotor R rotates, suction force caused by the ring magnet8 is always uniform and constant.

Further, as mentioned above, the press fitting process of the suctionring 11 into the motor base 5 never deforms the suction ring 11 or themotor base 5 other than the section to be press fitted, so that thesuction ring 11 is extremely accurate in perpendicularity and flatnesswith respect to an axis of rotation and accurately positioned.

Accordingly, the ring magnet 8 enables to be approached to the suctionring 11 furthermore, and resulting in enabling to minimizing dimensionsof the motor 50.

In addition thereto, noise, vibration or an amount of movement of therotor R in the axial direction is drastically reduced, so that the motor50 higher in reliability enables to be realized.

Second Embodiment

A motor 50A according to a second embodiment of the present invention isidentical to the motor 50 according to the first embodiment except forthe stator S, the motor base 5 and the suction ring 11, so that detailsof the motor 50A other than a stator, a motor base and a suction ringare omitted.

Firstly, referring back to FIG. 1, the motor 50A according to the secondembodiment is briefly explained. As shown in FIG. 1, the motor 50A iscomposed of a stator SA and the rotor R.

The stator SA is further composed of a motor base 5A, the sleeve 10, thecore 6 and the coil 7.

Further, a suction ring 11A in an annular shape is fixed to the motorbase 5A.

In reference to FIG. 4, the motor base 5A and the suction ring 11Aaccording to the second embodiment are depicted next.

FIG. 4 is a plan view of the suction ring 11A and the motor base 5Aaccording to the second embodiment of the present invention showing astate of press fitting the suction ring 11A into the motor base 5A.

In the case of the suction ring 11 according to the first embodiment,the suction ring 11 is provided with the protruded sections 11 a, whichdeform when the suction ring 11 is press fitted into the motor base 5.

On the contrary, in the case of the suction ring 11A according to thesecond embodiment, the suction ring 11A is not provided with anyprotruded sections. It shall be understood that such a protrudedsection, which deforms when press fitted, enables to be provided for themotor base 5A side.

For the purpose of easier understanding, a part equivalent to an overlapwidth for press fitting before press fitting is exhibited by a dottedline in an exaggerated form in FIG. 4.

In addition thereto, major dimensions of the suction ring 11A areidentical to those of the suction ring 11 except for protruded sections11 a, so that the same dimensions as those shown in FIG. 2 are denotedby the same reference sings.

As shown in FIG. 4, the motor base 5A is provided with six protrudedsections 5Ae1, which protrude inward in the radial direction from aninner circumferential surface of a wall section 5Ae of the motor base5A, at an equiangular interval.

More specifically, an inner diameter φ₄ of the protruded sections 5Ae1is designed so as to be “φ₁−φ₄=25 μm”, wherein “φ₁=20 mm” the same asthat of the suction ring 11 according to the first embodiment.

Further, each tip width “d4” in a circumferential direction of a tipportion of the protruded sections 5Ae1 is designated to be 2.0 mm.

Furthermore, an inner diameter φ₅ of the wall section 5Ae is designatedto be 25 mm.

More, both ends of the tip portion of each protruded section 5Ae1 aregradually connected to the inner circumferential surface of the wallsection 5Ae by means of a curved section 5Af.

The suction ring 11A is fixed to the motor base 5A by press fitting anouter circumference of the suction ring 11A into the six protrudedsections 5Ae1 of the motor base 5A.

As mentioned above, the overlap width for press fitting is designated tobe 25 μm in diameter.

Further, the motor base 5A is provided with six protruded sections 5Ae1of which each tip width “d4” is designated to be 2.0 mm.

Furthermore, a ratio of a length L3 in a circumferential direction ofthe protruded sections 5Ae1 to a total circumferential length L2 of thesuction ring 11A is minimized.

Accordingly, the suction ring 11A and the motor base 5A other than asection to be press fitted enable to be released from deformation.

More specifically, in the second embodiment of the present invention,the total circumferential length L2 of the suction ring 11A is “φ₁×π=20mm×π≈62.8 mm” and the length L3 of the protruded sections 5Ae1 is “2.0mm×6=12 mm”, so that the ratio of L3 to L2 is “12/62.8=19.1(%)”.

In this connection, press fitting pressure of the suction ring 11Aaccording to the second embodiment becomes 16.4 N, which isapproximately 19.1% of 86 N that is the press fitting pressure basedupon the prier art, wherein the suction ring according to the prior artis provided with no protruded sections, and whole range of the outercircumference of the suction ring is press fitted into the motor basetotally.

Accordingly, deformation of the suction ring 11A or the motor base 5Adoes not become a problem.

In the second embodiment, the suction ring 11A has a width “w”, wherein“w=(φ₁−φ₂)/2”. The width “w” is wider than the width “wt” of theprojected area T of the ring magnet 8, wherein the projected area T is arange of the ring magnet 8 that is projected on the surface of thesuction ring 11A. The suction ring 11A is formed in an annular shape soas to contain the whole range of the projected area T of the ring motor8 on the surface of the suction ring 11A and mounted on the motor base5A. Consequently, no matter how the rotor R rotates, suction forcecaused by the ring magnet 8 is always uniform and constant.

Further, as mentioned above, the press fitting process of the suctionring 11A into the motor base 5A never deforms the suction ring 11A orthe motor base 5A other than the section to be press fitted, so that thesuction ring 11A is extremely accurate in perpendicularity and flatnesswith respect to an axis of rotation and accurately positioned.

Accordingly, the ring magnet 8 enables to be approached to the suctionring 11A furthermore, and resulting in enabling to minimizing dimensionsof the motor 50A.

In addition thereto, noise, vibration or an amount of movement of therotor R in the axial direction is drastically reduced, so that the motorhigher in reliability enables to be realized.

As mentioned above, according to the present invention, the suction ring11 or 11A is fixed to the motor base 5 or 5A by the press fittingprocess.

Further, a part to be deformed in response to the press fitting isformed as the protruded section 11 a or 5Ae1.

Furthermore, the ratio of the length L1 or L3 in the circumferentialdirection of the protruded sections 11 a or 5Ae1 to the totalcircumferential length L or L2 of the suction ring 11 or 11A isdesignated to be less than a ratio to be specified in accordance with amaterial used for the suction ring 11 or 11A.

Accordingly, the motor 50 or 50A, which is released from any deformationand further is high in reliability and excellent in characteristics ofanti-vibration and impact resistant, enables to be realized.

In addition thereto, the motor 50 or 50A is less in noise and vibrationand exhibits excellent rotational characteristics.

While the invention has been described above with reference to aspecific embodiment thereof, it is apparent that many changes,modifications and variations in configuration, materials and thearrangement of equipment and devices can be made without departing formthe invention concept disclosed herein.

For instance, it shall be understood that a number of protruded sectionsand a shape of the protruded sections are not limited to those asdisclosed in the first and second embodiments. It enables to bedesignated accordingly in response to a ratio of a circumferentiallength of the protruded sections to an outer circumferential length of asuction ring as mentioned above.

Further, it shall be understood that the projected area T of the ringmagnet 8 on the suction ring 11 or 11A is not limited to a specificposition in a radial direction on the surface of the suction ring 11 or11A, as long as a whole range of the projected area T is allocated onthe surface of the suction ring 11 or 11A completely. In other words,the protruded sections 11 a enable to be provided on any part of thesuction ring 11 as long as the protruded sections 11 a are not formed ina shape, which cuts in the projected area T partially when the protrudedsections 11 a are formed on the suction ring 11 a.

Furthermore, it shall be understood that the protruded sections 11 a arenot limited to be provided on the outer circumference of the suctionring 11. They enable to be formed in an inner circumferential section ofthe suction ring 11 so as to protrude inward. In this case, a motor baseto be press fitted with the protruded sections necessary to be providedwith a wall section that protrudes inside the suction ring, and theprotruded sections are press fitted into an outer circumferentialsurface of the wall section.

More, it shall be understood that the above-mentioned configuration isnot limited to the case of providing protruded sections in the suctionring. The same is applied to a case of providing protruded wall sectionsin a motor base.

Moreover, the first and second embodiments of the present invention aredescribed in a so-called shaft rotational type motor in which a shaft isfixed to a hub. However, the present invention is also applied for amotor in which a shaft is fixed to a motor base side is inserted into asleeve fixed to a hub side, that is, a so-called shaft fixed type motor.

In addition thereto, it will be apparent to those skilled in the artthat various modifications and variations could be made in the motor andthe disc drive apparatus field in the present invention withoutdeparting from the scope of the invention.

1. A motor comprising: a rotor having a hub and a ring magnet beingfixed to the hub; and a stator having a motor base and a suction ring inan annular shape made from a magnetic material being fixed to the motorbase, wherein the rotor is sustained rotatable freely with respect tothe stator through a bearing composed of a sleeve and a shaft beinginserted into the sleeve; wherein the motor base is provided with aplurality of protruded sections that is formed on a wall section of themotor base rising in an axial direction from a bottom of the motor basein a radial direction and rising toward the hub side; wherein theplurality of protruded sections is formed in a circumferential directionat prescribed intervals, wherein an outer circumferential section or aninner circumferential section of the suction ring is press fitted intothe plurality of protruded sections of the motor base and resulting infixing the suction ring to the motor base; wherein a section contactingwith the protruded section of the motor base and another section beingseparated from and confronting with the wall section of the motor baseare alternately disposed on the outer circumferential section or theinner circumferential section of the suction ring in the circumferentialdirection, and further wherein one surface of the suction ring isdisposed so as to coincide with a bottom surface of the ring magnet andcovering a whole range of a projected area of the ring magnet that isprojected on the surface of the suction ring.